Multiple Charge Controllers

mnittler

I currently have 10 each 300 watt solar panels (3000 watts) wired to a single Schneider MPPT 60-150 charge controller connected to 3 each 48vdc battery banks of Trojan T-105 batteries (225Ahr x 3 = 675 Ahr@20 Hr rating) feeding a Schneider XW6048 6000 watt continuous 12000 watt peak hybrid inverter.

I want to add 10 each 290 watt solar panels (2900 watt) to a 2nd Schneider MPPT 60-150 charge controller and connect to the same 3 battery banks.

I plan on programming the same model of charge controllers with identical parameters.
I will have the battery temperature compensation probe attached to the battery.

1. Do I program the charge controllers with identical parameters?

2. Will this work using multiple charge controllers connected to the same battery banks?

3. Can the combined 5900 watts of solar panels using 2 separate charge controllers put too much current into the batteries?
    (The XW6048 inverter will feed an auxillary panel after the batteries get full and if there is more power generated than can be used by the aux panel and the grid is present then the inverter will sell power to the grid). I am making an assumption here that if the grid is not present and the solar cells are generating more power than the aux panel can use and the batteries get full then the charge controller will do its part and shut down the charging.

4. What is the maximum amount of amps the combined 5900 watts of solar panels can generate realistically?

5. What is the maximum amount of amps the 3 banks of 48vdc T-105 battery banks can accept?
Recommended and then maximum amps without battery damage)
(My thinking was that even if a little over the maximum amps that when the sun comes up and the batteries start charging that before full sun hits the batteries will already be partially charged and power will be sent to the auxillary panel shortly after full sun?)

6. Can 5900 watts of solar be used charging 3 banks of T-105 batteries?

bill von novak

mnittler said:

6. Can 5900 watts of solar be used charging 3 banks of T-105 batteries?

Max charge rate for that battery bank is around 85 amps.  Your system will provide ~100 amps.  I'd use current limiting to limit max current to 85 amps or less.

Estragon

Actual production is really location specific. Whatever you're getting on your 3kw array should be proportionately similar for the new array, assuming similar mounting etc. If the old panels have been in use for several years, they may have lost a bit of potential, so the arrays might end up producing about the same.

Generally you would program both controllers the same. I don't know that controller, but I assume there will be a way to calibrate voltage, as you'll want both controllers to see the same battery voltage.

I doubt the arrays will be able to charge bank with too much current unless you're on top of a big mountain or something. Still, setting a limit (eg 85-90a) can't hurt.

When set up and charging with the high current, I would check individual battery/cell and connection temperatures with an infrared meter to see if there are any hot spots to indicate dicey connections etc. Checking balance with a clamp meter also may help.

mcgivor

mnittler said:

I currently have 10 each 300 watt solar panels (3000 watts) wired to a single Schneider MPPT 60-150 charge controller connected to 3 each 48vdc battery banks of Trojan T-105 batteries (225Ahr x 3 = 675 Ahr@20 Hr rating) feeding a Schneider XW6048 6000 watt continuous 12000 watt peak hybrid inverter.

I want to add 10 each 290 watt solar panels (2900 watt) to a 2nd Schneider MPPT 60-150 charge controller and connect to the same 3 battery banks.

I plan on programming the same model of charge controllers with identical parameters.
I will have the battery temperature compensation probe attached to the battery.

1. Do I program the charge controllers with identical parameters?

2. Will this work using multiple charge controllers connected to the same battery banks?

3. Can the combined 5900 watts of solar panels using 2 separate charge controllers put too much current into the batteries?
    (The XW6048 inverter will feed an auxillary panel after the batteries get full and if there is more power generated than can be used by the aux panel and the grid is present then the inverter will sell power to the grid). I am making an assumption here that if the grid is not present and the solar cells are generating more power than the aux panel can use and the batteries get full then the charge controller will do its part and shut down the charging.

4. What is the maximum amount of amps the combined 5900 watts of solar panels can generate realistically?

5. What is the maximum amount of amps the 3 banks of 48vdc T-105 battery banks can accept?
Recommended and then maximum amps without battery damage)
(My thinking was that even if a little over the maximum amps that when the sun comes up and the batteries start charging that before full sun hits the batteries will already be partially charged and power will be sent to the auxillary panel shortly after full sun?)

6. Can 5900 watts of solar be used charging 3 banks of T-105 batteries?

1. Program identically
2. Yes, but each must have its own separate array 
3. Current output to battery can be limited in setup, not sure about the effect limitations have on the GT side, but it would be reasonable to assume, whatever the CC are set up to pass through.
4. Many factors influence the output, location, temperature etc. 75% of rated outputwould be a good starting point 

Although not familiar with the XW 6048, it wouldn't surprise me if the charging current can be limited and excess diverted to grid, thereby using maximum production. They are very sophisticated units with many options, hopefully someone with direct experience can contribute.

new2PV

The charge controllers should be networked on the Xanbus network. One will be a primary controller and the 2nd will be secondary.  As the primary changes the float the 2nd controller will follow.   You can use the Aux out to dump loads ie water heating as the battery voltage increases to reduce the current to batteries.  The controller will output 3500 watts max,  no matter what panels you have connected.  You must not allow the pv current to exceed 48 amps under all conditions or 140 volts. Do you have the combox?

Dave Angelini

If you enable cascading it all the settings will be automatically copied to other devices.
if you have 2 exact model devices they must have different addresses.
The PV max current is limited by the controller, if exceeded it will do no harm.
You may have too little battery capacity for the amount of solar. See manual.
Read the battery specs for max current. You may need to limit or buy batteries before their time.

Lumisol

If your PV max is a lot higher than the controller can use, you waste a lot.

new2PV

"The PV max current is limited by the controller, if exceeded it will do no harm" 

Are you sure about this statement the manual says under no circumstances to exceed pv amps of 48A to meet NEC standards.  This will allow for 125% increases in current due to increased output under cold and sunny,  conditions.

BB.

It is MPPT controller that modulate the current (via PWM) through an inductor (buck type down converter typically) to control the output current.

I do not know if they can limit the input current too, or if you just have to have a higher Vmp array so that you get the maximum power in and not exceed the 48 amp input current (Power = Volts * Current).

-Bill

Dave Angelini

THEY HAVE SINCE I TESTED THEM BILL, AND DO ON A REGULAR BASIS WITH MY CLIENTS in many installations.
This is pretty common now BTW/
For offgrid it is better to minimize this for longevity of systems. However, it is acceptable and done commercially.
Sorry for the caps but I am way offgrid right now.........

new2PV

Interesting info. Its safe to run these units with more panels then?

Dave Angelini

Pretty common to over panel by 25%.
If you are offgrid, you are accepting the risk that you are pushing the electronics harder.

With a 5 year warranty on grid people/commercial apps accept the risk in many cases.  Just shut down a string in summer and use it for winter is an offgrid strategy that works for many.